For certain applications of electric fuses it is desirable to state so-called figures of merit which express certain characteristics of a particular type of fuse.
Such a figure of merit is the ratio of current-carrying capacity to i.sup.2 .multidot.t.
A fusible element in the form of a ribbon of copper of a given width having one short circuit neck in the center thereof has a given current-carrying capacity and the short circuit neck has a given i.sup.2 .multidot.t value. By increasing the heat-dissipating area of the ends of the fusible element relative to that of its center portion the current-carrying capacity of the fusible element can be greatly increased. It has now been discovered that to achieve this the end portions of the fusible element must be made non-planar, e.g., U-shaped, while the center portion must remain substantially planar. The i.sup.2 .multidot.t of the center portion can be minimized by making the center portion of silver rather than of copper.
Thus, the figure of merit which is the ratio of current-carrying capacity to i.sup.2 .multidot.t can be greatly increased by increasing the numerator and descreasing the denominator of this fraction.